There are many situations where it is desirable to locate buried utilities or other objects, such as pipes and cables. For example, prior to starting any new construction that involves excavation, it is important to locate buried objects and underground utilities, such as power lines, gas lines, phone lines, fiber optic cable conduits, cable television (CATV) cables, sprinkler control wiring, water pipes, sewer pipes, and the like (collectively and individually referred to herein as “utilities” or “objects”). As used herein, the term “buried” refers not only to objects below the surface of the ground, but also to objects located inside walls, between floors in multi-story buildings, cast into concrete slabs, or otherwise obscured, covered, or hidden from direct view or access.
Location of these buried objects may be important for cost, time, and safety reasons. For example, if a backhoe or other excavation equipment hits a high voltage line or a gas line, serious injury may result. Further, severing water mains and sewer lines leads to messy cleanups.
Buried objects can be located by sensing an emitted electromagnetic signal. For example, some buried cables, such as electric power lines, are already energized and emit their own long cylindrical electromagnetic field. In other cases, the buried object may be energized to produce electromagnetic radiation. For example, an external electrical power source having, for example, a frequency in a range of approximately 22 Hz to 500 kHz may be used to energize a buried object such as a pipe or conduit. Location of buried long conductors is often referred to as “line tracing,” and the results may be referred to as a “locate.”